I'll start by saying that two things irk me. 1) people assuming this is a sequel to The Exorcist. Its clearly not. 2) Mockumentary horror films... they're so common these days that their effectiveness succumbs to the gimmickry. The Last Exorcism is the latest pseudo doco which was championed by Eli Roth (Cabin Fever, Hostel). I'm pleased to say that it actually works quite well. Exorcism movies are tough to pull off, after all the benchmark is astronomically high. The ones that work are the ones which deliver something different. Of recent memory The Exorcism Of Emily Rose was one such movie. In this one, the shaky doco feel adds to it's creepiness with spooky moments catching both the characters and the viewers off guard. I think what also works in it's favour is that the characters stop talking to the camera early in the film and it plays out more like a regular narrative. The 3rd act was a nice surprise to me and the plot developments were courageous for a genre where we've assumedly seen it all. Not original by any means, but a fresh take on a generic genre using an exhausted formula.